Rochester 2 Jet 4 Jet Power Piston Assembly - 85-800

Rochester 2-Jet / 4-Jet Power Piston Assembly (Part #85-800)

Meta Title: Rochester Power Piston Assembly 85-800 | 2-Jet & 4-Jet Carburetors
Meta Description: Genuine Rochester power piston assembly #85-800 fits 1955-73 Chevrolet, Buick, Pontiac, Olds. Ensures smooth fuel delivery in power mode. In stock and ready to ship.

Product Highlights

• Fits Models: Rochester 2-Jet/4-Jet (2-barrel and 4-barrel) carburetors

• OEM Replacements: Includes correct dimensions to replace OE #7006011 or #7009718

• Ideal For: Classic GM vehicles—Chevy, Buick, Pontiac, Olds—from model years 1955–1973

What It Does & How It Works

This power piston works in conjunction with the power valve circuit:

1. High Vacuum (Idle/Light Throttle): Holds piston up—power jet closed.

2. Low Vacuum (Acceleration/Heavy Load): Piston drops—opens power jet—adds extra fuel for better acceleration

Technical Specifications

• Length: Typically 2.30–2.37? total. Slight length variations are acceptable if the diameter matches

• Diameter: Precision-matched to factory OEM for seamless fit.

• Movement: Should slide freely—ensure piston bore is clean and lubricated

Installation Instructions

1. Clean the power piston bore thoroughly; using silicone spray or light lubrication is recommended.

2. Insert the piston assembly.

3. Secure by staking the bore.

Why Choose Part 85-800?

• Exact OEM Fit: Replaces OE numbers 7006011 / 7009718, guaranteeing factory-level performance

• Hard-To-Find Genuine Part: Ideal for vintage carburetor rebuilds—especially sought for restored classic cars.

• Positive Customer Feedback:

  • “Part was exactly as ordered. Perfect fit.”

  • “Improved, wider base… fit well. No problems.”

Frequently Asked Questions

Q: When will this ship?
A: Orders typically ship same day if ordered before 12 noon. We process and fulfill Monday through Friday, excluding holidays. Tracking information is emailed as soon as your item ships.

Q: Does this fit 2 Jet marine carburetors?
A: NO, verify the piston diameter and overall length against your existing part or reference the carburetor number.

Q: Can I use a slightly longer piston?
A: Yes. Pistons ranging from 2.30? to 2.37? in length are considered compatible as long as the diameter matches your bore.

Q: My bore is corroded—what should I do?
A: Use crocus cloth or a fine polishing tool to clean the bore. Make sure the piston moves freely before installation. A light silicone lubricant can help ensure smooth movement.

Clean out the hole, using silicon spray lubricant.
Insert the piston.
Stake the hole to keep the piston from coming out.
Make sure your power jets has a straight pin. Replace if bent.